Air filters

Claim 1

A self cleaning air filter unit comprising an inlet chamber and an outlet chamber, a filter wall arranged in a horizontal plane to separate the inlet chamber from the outlet chamber, a plurality of filter elements arranged on the filter wall in an array of cross-wise rows over a length of the filter wall to allow air to pass from the inlet chamber to the outlet chamber through the filter elements, each said filter element comprising a filter sleeve sealed around one end to the periphery of an aperture in said filter wall and closed at the other end, and an open lattice cylindrical support cage arranged within the sleeve and mounted on said filter wall, said one end of each of said filter sleeves being provided with a resilient annular former, the material of the sleeve being rolled over the former and reinforced at that point, and said support cages being each provided with a flange, said flange being arranged to grip said former between itself and a face of said filter wall, a plurality of clamping plates each releasably attached to said filter wall and arranged to engage and retain a plurality of said support cages, a gantry arranged in the outlet chamber across said array for traverse along the length of the array, a plurality of reverse air flow nozzles arranged on the gantry to register successively with the filter elements of each row of the filter elements, a manifold having an inlet port mounted on said gantry and arranged to distribute air from the inlet port to said nozzles, the nozzles being mounted along a face of the manifold opposed to said filter wall, a flexible curtain arranged on the gantry around the outlets of all said nozzles to form a shroud therearound, the curtain extending substantially to said filter wall, and means for supplying air to the nozzles to exit therefrom at such speed that in use of the filter unit the flow of air from the inlet chamber to the outlet chamber is reversed through a filter element when it is in alignment with a nozzle, said air supply means comprising an electrically driven fan unit mounted outside said outlet chamber and movable ducting connecting said inlet port of the manifold to said fan unit.